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General Ecology, factors, biomes

Range and dispersal

Interactions lead to organism andpopulation range limits and dispersallimits. Both biotic and abiotic factors can‘limit’ or define these.

Case: mussels in the intertidalCase: Mazzaella parksii: a red intertidal alga.

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Community structureFigure 3.23

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Species tolerance• Law of tolerance: the existence, abundance and

distribution of a species in an ecosystem are (largely)determined by whether the levels of one or morefactors (abiotic) falls within the range of tolerance

• Tolerance to abiotic and biotic factors in partdetermines the range/distribution

Tolerance Cont.

• Acclimation: animal or plant is able toadjust to changes.– Some examples?

• Threshold effect:builds up with littleresponse until sudden inability to cope– Some examples?

Tolerance Cont.

• Physiological responses• Morphological responses• Behavioral responses

• Community boundaries?

• Short term and long term

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Abiotic factors are important indetermining ecosystem structure

• Living things have tolerance limits toabiotic factors such as…?

Species Interactions (Biotic):Interspecific and Intraspecific

• Competition• Predation• Symbiosis

Range explanations

• A species never dispersed beyond its presentboundaries

• Pioneers failed to survive• Range has been reduced over evolutionary time• Pioneers became isolated/separated:phylogeography

Behavioral responses

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Tolerance limitsFigure 3.2

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•Survival and differential reproductivesuccess over a period of time

•Traits that increase ‘fitness’ are ‘selectedfor’, and are passed on through generations

Adaptation by the processof Natural Selection

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In tundra habitats above timberline, the alpine skypilot is pollinated primarily by bumblebees.

In forested habitats below timberline, the alpine skypilot is pollinated primarily by flies.

Below-timberline flower: small and skunky-smelling Flower size (mm)

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Tundra flower: big and sweet-smelling

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Figure 50.2 Patterns of distribution in the biosphere

Biomes

• What defines a biome?• Where are the ‘lines’ drawn?• What are the major controlling factors?• What about aquatic ‘biomes’

Biomes• Animals and plants have narrowranges of tolerance to abiotic factors

• This in part determines the bioticcomponents of biomes. These arebroad geographic regions determinedby temperature and rainfall, anddescribed by their plant communities

Figure 50.3 A climograph for some major kinds of ecosystems (biomes) in NorthAmerica

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World biome mapFigure 5.3

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Biome climate graphsFigure 5.4

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Figure 50.4 Solar radiation and latitude

Figure 50.5 The cause of the seasons Figure 50.6a Global air circulation, precipitation, and winds

Figure 50.6b Global air circulation, precipitation, and winds Figure 50.7 Rain shadows

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Figure 50.8 Lake stratification and seasonal turnover

Global winds

Aquatic Biomes

• Temperature• Currents• Nutrients• Salinity• Oxygen• Depth• Sunlight

• Physical as well as chemical boundaries

•Oligotrophic•Eutrophic•Turnover rate

Figure 50.8 Lake stratification and seasonal turnover

Figure 50.9 The distribution of major aquatic biomes Figure 50.13 Zonation in the marine environment

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Sea surface temperature

Currents Biomes

• What defines a biome?• Where are the ‘lines’ drawn?• What are the major controlling factors?• What about aquatic ‘biomes’

Some Key Points• Animals interact with biotic and abiotic factors in ways

which shape their survival and distributions• Biomes are delineated by abiotic factors, but biotic factors

play a role too.• Biomes are described by plant communities which are

‘controlled’ by temperature and precipitation• Oceans are different: currents and salinity/oxygen

distribution have a major impact - productivity• Organisms have tolerance ranges to abiotic factors - both

long term and short term effects.